A conventional generator for generating electric power with its permanent magnets rotated by an external driving force has its permanent magnets arranged of a drum shape.
However, such conventional generator has a problem that an efficiency of the power generation is low by reasons, for example a rotator with the drum shape permanent magnets is heavy and so on. It has another problem that an efficiency of heat radiation is low because of the rotator with the drum shaped permanent magnets and a stator with windings are coaxially arranged.
Hence, an object of the present invention is to provide a generator there the permanent magnets are rotated by an external driving force for generating electric power at higher efficiency and with improvement of heat radiation.